What happened
On 29 January 2024, a Beechcraft King Air C90A, registration ZS-FON, was performing a private flight from Lanseria International Aerodrome to Bona-Bona Game Lodge Airfield. The flight, operated under Part 9 and involving a pilot and two passengers, proceeded without incident until the landing phase on Runway 17.
During the landing roll, the left main wheel assembly detached from its axle. This separation caused the aircraft to veer sharply to the left. Despite the pilot's attempts to correct the yaw using right rudder and applying brakes, the aircraft continued off the runway, coming to a stop in a grass area just one meter from the runway edge. The departing wheel assembly struck the No. 1 propeller blades, causing significant damage to the propeller, wheel hubs, and the left main landing gear strut. There were no injuries to the occupants.
The investigation
SACAA AIID investigators examined the wreckage and conducted laboratory analysis of the failed components. The investigation focused on the mechanical integrity of the landing gear assembly. The aircraft had completed a mandatory periodic inspection only 14.6 hours prior to the accident, and all relevant certificates, including the airworthiness and pilot's medical, were valid.
Findings
Technical analysis revealed that a fracture had developed on the front face rib of the left main wheel's outer cone-bearing inner ring. This fracture led to the disintegration of the bearing assembly during operation. The investigation noted that the failure was likely due to a pre-existing fracture that was undetectable through standard maintenance inspections. The fracture morphology suggested the crack may have been present since an undetermined period prior to the accident, potentially linked to manufacturing discrepancies.
Safety action
Following the findings, a safety recommendation was issued for the manufacturer to review its maintenance programs. The goal is to ensure that critical components are subject to appropriate mandatory inspections, specifically incorporating non-destructive testing (NDT) methods for effective crack detection.